Barry Steakfries is a struggling salesman, on the verge of losing his job if he doesn't sell any gramophones. But when he sees a machine-gun jetpack by Legitimate Research, a science facility run by Really Bad Corp, he steals it, a robot dog and a shotgun and decides to save the world using them against a zombie invasion across time by the evil Professor Brains.
(This also adapts Age of Zombies.)